This is caused when another instance is currently mounting the database. An
instance tried to mount the database in exclusive mode, but some other
instance has already mounted the database in exclusive or parallel mode.

Either mount the database in parallel mode or shut down all other instances
before mounting the database in exclusive mode.

Aby,=0D
A database is started in EXCLUSIVE mode by default. Therefore, the

ORA-01102 error is misleading and may have occurred due to one of the

following reasons: =0D
- there is still an "sgadef<sid>.dbf" file in the "ORACLE_HOME/dbs"

directory (if you are on unix box)=0D
- the processes for Oracle (pmon, smon, lgwr and dbwr) still exist =0D
- shared memory segments and semaphores still exist even though the

database has been shutdown =0D
- there is a "ORACLE_HOME/dbs/lk<sid>" file (if you are on unix box)=0D
=0D
Verify that the database was shutdown cleanly by doing the following: =0D
1. Verify that there is not a "sgadef<sid>.dbf" file in the directory

ORACLE_HOME/dbs". If this file does exist, remove it. =0D
2. Verify that there are no background processes owned by "oracle" . If
background processes exist, remove them =0D
3. Verify that no shared memory segments and semaphores that are owned by
"oracle" still exist .=0D
If there are shared memory segments and semaphores owned by "oracle",